(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method and apparatus for the drying of wafers.
(2) Description of the Prior Art
In the creation of semiconductor devices, these devices are typically created in or on the surface of a semiconductor wafer. After the process of creating the devices in or on the surface of the wafer and also during intervening processing steps, the need arises for drying the surface of the wafer. One of the conventional methods that is used for this purpose is the application of a cascade rinse whereby the wafer is placed into a water supply that is provided in an inner chamber while the rinsing water is transferred from an outer chamber to the inner chamber. This causes problems of water purity since there is an interconnect between the various chambers of the rinsing apparatus. Further, even after the process of cleaning the wafer has been completed, the wafer must as yet be dried, which may again be a source of introducing foreign matter (contaminants) onto the surface of the wafer.
Other methods employ the quick insertion of the wafer into a tank containing water in order to remove contaminants and other impurities in one, quick operation. Since particles that need to be removed from a surface must at times be agitated before the particle is loosened from the surface and can then be removed, this method of wafer cleaning has also proven to be not satisfactory.
Yet another method relies on spinning the wafer at high speed while water is applied to the surface of the wafer. Dislodged particles are in this manner removed from the surface of the wafer by centrifugal force, a step of drying the wafer can be applied as part of this sequence. This method requires rather complex supporting tools and equipment and, due to the violent nature of the process, the degree of particle removal is difficult to control.
Yet another method uses an isopropyl alcohol (IPA) vapor dryer or a full displacement IPA dryer. These methods typically require large amounts of IPA in order to achieve drying the wafer satisfactorily. In addition, to completely dry a wafer using this method requires a large drying time, adding to product costs. Also, the method of IPA vapor dry requires a high temperature of in excess of 200 degrees C. adding to the thermal budget of the process.
There is therefore a need in the industry to provide a method of cleaning and drying wafers that is cost-effective (low thermal requirements and limiting the need for a cleaning agent such as IPA) and that is simple to operate (low equipment cost). The invention provides such a method by reducing the temperature that is required to dry a wafer while heating and the drying of the wafer will be achieved using energy from a microwave source.
U.S. Pat. No. 6,200,387 (Ni) shows a nebulizer and megasonic system using IPA.
U.S. Pat. No. 6,219,936 (Kedo et al.) shows a drying process using IPA and an ultrasonic nebulizer, see cols. 4, 6-8.
U.S. Pat. No. 6,119,367 (Kamikawa et al.), U.S. Pat. No. 6,128,829 (Wolke et al.), U.S. Pat No. 6,004,239 (Wong et al.) and U.S. Pat. No. 5,656,329 (Hampden-Smith et al.) are related patents involving misters, IPA, sonics and drying wafers.
A principle objective of the invention is to provide a cost-effective method and apparatus for the cleaning and drying of a wafer.
Another objective of the invention is to limit the thermal budget that is required for the cleaning and drying of a wafer.
Yet another objective of the invention is to provide a method and apparatus for cleaning and drying a wafer that requires a limited amount of cleaning agent.
A still further objective of the invention is to provide a method and apparatus for cleaning and drying a wafer that can be completed in a relatively short period of time.
In accordance with the objectives of the invention a new method and apparatus is provided for the cleaning and drying of a wafer. An IPA vapor is created using an ultrasonic nebulizer that can be operated at a relatively low temperature. The water and the IPA that is used by the cleaning and drying process will be heated and evaporated using energy supplied by a microwave source of energy.